This invention relates to an agricultural pneumatic tire. More particularly, this invention relates to a class of agricultural tires known as irrigation tires.
Irrigation tires are used in specially designed irrigation apparatus. The tires support the sections of piping Each section spans from 80 feet to 124 feet and enough sections can be attached together to span one-quarter mile. The apparatus pivots about a well head or water supply and can traverse 360.degree. yielding a circular irrigated field having a diameter of one-half mile. Each such system uses twenty tires, two tires at each support truss.
The tires employed in such a system simply must be able to support the plumbing or irrigation pipe's weight and provide sufficient traction to move the irrigation apparatus at very slow speeds sometimes measured in minutes per revolution.
The tires are designed for maximum cost efficiency. The carcass of an irrigation tire is generally constructed of only two bias plies wrapped around a pair of beads; no reinforcing belts are used. The tires have a nominal rim diameter of 24.00 inches (61 cm) or greater and an overall diameter of about 43 to 58 inches (109 cm to 147 cm), depending on rim size. The tread has an inner tread and tread lugs having a depth less than the regular R1 depth as defined in the 1992 Tire and Rim Association, Inc. Yearbook, and as used in shallow nonskid tires. That is in tires having a nonskid level of less than 100. The nonskid, being the height of the lug element to the inner tread surface as measured by any of the common means known in the art. The level 100 means the recommended height of the lugs as set forth in the Engineering Design Information standard of the U.S. Tire & Rim Associations. Any greater or lesser depth would be indicated as a percentage of this standard. For example, a height which would be 90% of this level would be a 90 non skid.
The prior art irrigation tires were historically produced from obsolete rear farm tire molds. Due to the increased demand for irrigation in dry regions of the world, the number of irrigation tires sold has increased, warranting a design specifically suited to this use.